Mountain pine beetle activity was monitored in one set of
2.5 acre plots in the southern por-tion of the Black Hills National
Forest over a 17-year period. Beetles attacked 77 percent of
the trees in the uncut control, 48 percent of the trees in the
growing stock level (GSL) 100/110, 53 percent of the trees in
the GSL 80/90, and 9 percent of the trees in the GSL 60/70. The
percentages of MPB-attacked trees in each 1 in diameter class
were lowest in the GSL 60/70, intermediate in the GSL 80/90 and
GSL 100/110, and highest in the uncut control. Live basal area
was significantly reduced in the GSL 80/90, GSL 100/110, and
control but not in the GSL 60/70. Partial cutting to reduce beetle-caused
mortality may be ineffective for partially cut parcels of <10
acres if the partially cut stands are surrounded by unman-aged
susceptible stands. To increase the effectiveness of partial
cutting, stands should be managed on a landscape basis. A 100-ft-wide
strip with stand density of less than or equal to GSL 70 between
unmanaged and man-aged stands may be sufficient to limit the
spread of beetle-caused mortality from unmanaged stands to adjacent
partially cut stands.